1. Field of the Disclosure
The disclosure relates generally to micromechanical devices or micro-electromechanical systems (MEMS) and, more particularly, to micromechanical or MEMS resonators.
2. Brief Description of Related Technology
Micromechanical resonators have been constructed in accordance with so-called “free-free” designs. A free-free beam resonator contrasts from, for instance, a clamped-clamped beam resonator in which a resonant beam is clamped, or anchored, at the ends of the beam. Free-free beam resonators are typically fabricated via surface micromachining processes, vibrate in a direction vertically relative to the substrate, and exhibit good resonance performance for MEMS timing products.
Free-free beam resonator designs have utilized short support structures. Examples of free-free beam resonators with short support structures are described in U.S. Pat. No. 6,930,569, the entire disclosure of which is hereby incorporated by reference.
Some free-free beam resonator designs have presented drawbacks in performance, including inadequate power handling (or linearity) in which the output frequency varies at a level around −20 dBm. In contrast, quartz crystal resonators often operate at a level of 0 dBm. Improvements in power handling may lead to better phase noise performance of an oscillator driven by the resonator. As a result, MEMS oscillators have often exhibited worse phase noise than quartz crystal oscillators.